Sciencemadness Discussion Board
Not logged in [Login ]
Search the forums Search   Frequently Asked Questions FAQ   View member list Member List   Today's Posts Today's Posts   Forum Stats Stats Back to: sciencemadness.org
Sciencemadness Discussion Board » Engineering and Equipment » Reagents and Apparatus Acquisition » Starch-Iodide Test Papers Go To Bottom

Printable Version  
 Pages:  1  2
Author: Subject: Starch-Iodide Test Papers
Sulaiman
International Hazard
*****



Posts: 3695
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline


[*] posted on 16-9-2016 at 13:58


I noticed on the nitrite Wikipedia page

"Sodium nitrite is made industrially by passing "nitrous fumes" into aqueous sodium hydroxide or sodium carbonate solution"

so next time I need to get rid of NOx fumes i know what to do :)



CAUTION : Hobby Chemist, not Professional or even Amateur
View user's profile View All Posts By User
aga
Forum Drunkard
*****



Posts: 7030
Registered: 25-3-2014
Member Is Offline


[*] posted on 17-9-2016 at 08:28


Hmm. Tried cold NaNO2 solution with both HCl and H2SO4 and just got some more brown gas.

There *may* have been a faint 1mm deep ring of blue floating on top of the liquid for a second, but that could have been a trick of the light.



View user's profile View All Posts By User
aga
Forum Drunkard
*****



Posts: 7030
Registered: 25-3-2014
Member Is Offline


[*] posted on 26-11-2016 at 02:44


After all the messing about, i discovered today that i simply did not know how to use starch-iodide papers properly.

Turns out that they need to be wetted with a 1% HCl solution first.

http://chestofbooks.com/science/chemistry/Processes-Dye-Chem...

Doing that with one of the remaining papers (wasted most of them) it went dark blue with 1 drop of a very dilute NaNO2 solution.

The nitrite and the papers were both actually OK from the beginning !

Edit:

If i'd understood what Magpie said earlier, i'd have known sooner.

[Edited on 26-11-2016 by aga]



View user's profile View All Posts By User
S.C. Wack
bibliomaster
*****



Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline

Mood: Enhanced

[*] posted on 26-11-2016 at 06:30


In the usual usage the solution to be tested is already acidic and may even need to be diluted with water before dropping it on the paper.



"You're going to be all right, kid...Everything's under control." Yossarian, to Snowden
View user's profile Visit user's homepage View All Posts By User
aga
Forum Drunkard
*****



Posts: 7030
Registered: 25-3-2014
Member Is Offline


[*] posted on 26-11-2016 at 11:06


Quote: Originally posted by S.C. Wack  
In the usual usage the solution to be tested is already acidic

Thank you for that info.

So obvious now i think about it, yet i've been hung up on this for months !

In retrospect, i think i went wrong by thinking of an 'indicator' as something magical, and not just another a chemical reaction.



View user's profile View All Posts By User
Acuyo
Harmless
*



Posts: 29
Registered: 29-6-2016
Member Is Offline

Mood: activated

[*] posted on 6-3-2017 at 20:19
Sodium Iodide?

Can this preparation be done with naoh instead of koh, or is potassium necessary?
View user's profile View All Posts By User
 Pages:  1  2

 Sciencemadness Discussion Board » Engineering and Equipment » Reagents and Apparatus Acquisition » Starch-Iodide Test Papers   Go To Top